Chlamydia

Chlamydia is a common sexually transmitted infection (STI) caused by the bacterium Chlamydia trachomatis. It is one of the most frequently reported bacterial STIs globally, often asymptomatic but capable of causing serious reproductive complications if left untreated.

Etiology and Transmission

The causative agent, Chlamydia trachomatis, is an obligate intracellular bacterium with a unique biphasic developmental cycle involving infectious elementary bodies and replicative reticulate bodies. Transmission occurs primarily through unprotected vaginal, anal, or oral sexual contact with an infected person. It can also be transmitted from an infected mother to her newborn during childbirth, potentially causing neonatal conjunctivitis or pneumonia. The bacteria infect columnar epithelial cells of the urethra, cervix, rectum, pharynx, and conjunctiva.

Epidemiology

Chlamydia is the most commonly reported notifiable infectious disease in many countries, including the United States. Infection rates are highest among sexually active adolescents and young adults under 25 years of age. Factors contributing to its prevalence include the high frequency of asymptomatic infections, which facilitate unknowing transmission, and barriers to routine screening. Disparities exist, with higher reported rates often observed among certain racial and ethnic minority groups, largely attributed to social determinants of health and healthcare access rather than biological factors.

Clinical Presentation and Symptoms

A significant proportion of infections—estimated at up to 70-80% in women and 50% in men—are asymptomatic. When symptoms do occur, they typically appear 1 to 3 weeks after exposure.

• In women: Symptoms may include abnormal vaginal discharge, a burning sensation during urination, pain during intercourse, intermenstrual or postcoital bleeding, and lower abdominal pain. The primary sites of infection are the endocervix and urethra.
• In men: Symptoms often consist of a penile discharge (which may be clear or cloudy), dysuria (painful urination), and less commonly, testicular pain or swelling indicative of epididymitis.
• Rectal infections: Can occur in both men and women and may cause rectal pain, discharge, or bleeding, though they are frequently asymptomatic.
• Pharyngeal infections: Usually asymptomatic but can occasionally cause a sore throat.

Complications

Untreated chlamydial infection can lead to severe and often irreversible sequelae, particularly in women.

• Pelvic Inflammatory Disease (PID): A serious complication where the infection ascends from the cervix or vagina to the upper genital tract, affecting the uterus, fallopian tubes, and ovaries. PID can cause chronic pelvic pain, tubal factor infertility, and increase the risk of ectopic pregnancy.
• Reactive Arthritis: Formerly known as Reiter's syndrome, this can occur following chlamydial infection, characterized by arthritis, conjunctivitis, and urethritis.
• Increased HIV Risk: The genital inflammation caused by chlamydia can increase susceptibility to and transmission of HIV.
• Pregnancy Complications: Infection during pregnancy is associated with preterm delivery, low birth weight, and postpartum endometritis. Neonatal transmission can result in conjunctivitis (ophthalmia neonatorum) and pneumonia in the newborn.
• In men, complications include epididymo-orchitis (inflammation of the epididymis and testicles), which can lead to infertility in rare cases.

Diagnosis

Diagnosis is typically performed using nucleic acid amplification tests (NAATs), which are highly sensitive and specific. NAATs can be performed on urine samples (in both men and women) or clinician-collected swabs from the endocervix, vagina, male urethra, rectum, or pharynx. Self-collected vaginal swabs are also a reliable and acceptable method. Culture, once the gold standard, is now rarely used due to its technical difficulty but may be employed in specific legal or medical situations. Screening is recommended annually for all sexually active women under 25 and for older women with risk factors (e.g., new or multiple partners). Screening for sexually active young men is considered in high-prevalence settings.

Treatment and Management

Chlamydia is curable with appropriate antibiotic therapy. The recommended first-line regimens are:

• Azithromycin (1 gram orally in a single dose), or
• Doxycycline (100 mg orally twice daily for 7 days).

Alternative regimens include levofloxacin or erythromycin. All sexual partners within the 60 days preceding symptom onset or diagnosis should be tested and treated to prevent reinfection and further transmission. Patients are advised to abstain from sexual activity for 7 days after single-dose therapy or until completion of a 7-day regimen and resolution of symptoms. A test-of-cure (repeat testing) is not routinely recommended for non-pregnant persons completing first-line therapy but is advised for pregnant women, typically 3-4 weeks after treatment completion. Reinfection is common, highlighting the importance of partner treatment and repeat screening 3-6 months after initial treatment.

Prevention

Preventive strategies include:

• Consistent and correct use of latex or polyurethane condoms during sexual activity.
• Mutual monogamy with an uninfected partner.
• Regular screening for sexually active individuals in recommended age and risk groups.
• Expedited Partner Therapy (EPT), where permitted, allowing healthcare providers to prescribe or provide medication for the patient's partner without a clinical evaluation.
• Public health education to increase awareness about asymptomatic infection and the importance of screening.